Yokogawa PH72 Personal pH/ORP Meter - Manual (Page 52)

IM 12B03D02-01E
6-3
6. Maintenance
F0602.EPS
Soak in 0.1 mol/l hydrochloric acid
0.1 mol/l dilute
hydrochloric acid Cleaning water
After 10 to 20
minutes
Rinse thoroughly in water
Figure 6.2 Acid Cleaning
6.3 Sensor Replacement
Since a pH sensor undergoes chemical changes with time, its performance deteriorates
gradually. Under normal operating conditions a sensor can be used for one or two years.
Sensor deterioration, however, speeds up depending on the nature of a sample solution,
e.g., a high temperature solution. Storage conditions also affect the sensor life.
If or appears while calibration is being performed with a sensor for
which is displayed, replace the sensor.
6.4 Rehydrating the Glass Electrode
A dry glass electrode gives fluctuating pH readings. If a glass electrode has dried up,
soak it in water (tap water) for 1 to 2 hours or longer to rehydrate. The sensor will give
stable pH readings.